In the U.S., black infants are 2.4 times as likely to die as white infants, and are more likely to experience adverse birth outcomes that contribute to morbidity and mortality. Black women are also more likely than whites to be obese at conception and to gain outside the Institute of Medicine (IOM) recommended gestational weight gain ranges. Pregravid obesity dramatically increases risk of poor birth outcomes, but these effects may be lessened by appropriate weight gain. Unfortunately, the 2009 Institute of Medicine Committee to Reevaluate Pregnancy Weight Gain Guidelines was unable to answer some of the most important questions about optimal gestational weight gain because of a lack of research data. Our project seeks to address his urgent need. We propose to test the hypotheses that optimal gestational weight gain declines as prepregnancy BMI increases, and that BMI and weight gain are contributors to the black-white disparity in infant mortality and adverse birth outcomes. Our study design will employ existing Pennsylvania vital records (2003-2008) reflecting 751,000 births to black and white mothers. This project seeks to explore separately for black and white women in each BMI category the range of total weight gain that is associated with optimal outcomes and balances risks of low and high weight gain in this population. The project also will determine the contribution of prepregnancy BMI and pregnancy weight gain to the black-white disparity in adverse pregnancy and infant outcomes (preterm birth; small-for-gestational age birth; large-for-gestational age birth; unplanned Cesarean delivery; and infant mortality). The successful completion of these Aims will answer an important question: How do maternal pregravid weight and weight gain during pregnancy-two potentially modifiable factors-contribute to the racial disparity observed in infant mortality rates and adverse birth outcomes? Our use of vital records data leverages an untapped resource to explore a research question of major public health importance. Importantly, this study also seeks to inform the contentious debate regarding ideal gestational weight gain in severely obese women. It will explicitly examine the safety of no weight gain or weight loss during pregnancy for the infant.